Study Questions:

What is the diagnostic accuracy of dobutamine stress cardiac magnetic resonance imaging (DSCMR) as compared to dobutamine stress echocardiography (DSE) in patients with left bundle branch block (LBBB)?

Methods:

This prospective study performed DSCMR and DSE in 82 consecutive patients with LBBB referred to a cardiology clinic for suspected coronary artery disease (CAD). All patients underwent DSCMR, DSE, and invasive coronary angiography (ICA), and the diagnostic accuracy of DSCMR and DSE were compared to ICA detection of obstructive CAD (≥70% stenosis or ≥50% stenosis of left main artery). All patients had angina and at least one cardiovascular risk factor; patients with known CAD or contraindications to testing were excluded. All studies were interpreted by two blinded readers, with a third reader used to adjudicate as needed.

Results:

Mean age was 57 ± 8 years, and 65% were male. Obstructive CAD was observed in 41% of subjects. The sensitivity, specificity, positive predictive value, and negative predictive value were 71%, 73%, 65%, and 78% for DSE; 71%, 88%, 80%, and 81% for cine-only DSCMR; 71%, 94%, 89%, and 82% for first-pass perfusion-only DSCMR; 42%, 100%, 100%, and 68% for late-gadolinium enhancement-only DSCMR; and finally 82%, 96%, 93%, and 89% for comprehensive DSCMR.

Conclusions:

The authors concluded that comprehensive DSCMR has a markedly higher sensitivity and specificity than DSE in patients with LBBB and suspected CAD.

Perspective:

While stress echocardiography and single-photon emission computed tomography are often used to evaluate suspected CAD in patients with LBBB, they have known limitations, and LBBB may adversely affect study accuracy. This study demonstrates that cine-only DSCMR had similar sensitivity and higher specificity as compared to DSE. Furthermore, by adding additional imaging uniquely available with CMR – such as first-pass perfusion and late-gadolinium enhancement – a comprehensive DSCMR protocol resulted in markedly higher sensitivity and specificity. These findings suggest that DSCMR may be a reasonable diagnostic option to evaluate patients with LBBB and suspected CAD. It must be noted that these are results from a single center, that the cost-effectiveness of this approach is not known, and that the comparative diagnostic performance between DSCMR and exercise echocardiography were not examined.